ospfd: add support for suppress_fa

This command will trigger the OSPF forwarding address suppression in
translated type-5 LSAs, causing a NSSA ABR to use 0.0.0.0 as a forwarding
address instead of copying the address from the type-7 LSA

Example: In a topology like: R1 --- R2(ABR) --- R3(ASBR)

R3 is announcing a type-7 LSA that is translated to type-5 by the R2 ABR.
The forwarding address in the type-5 is by default copied from the type-7

    r1# sh ip os da external

                    AS External Link States

      LS age: 6
      Options: 0x2  : *|-|-|-|-|-|E|-
      LS Flags: 0x6
      LS Type: AS-external-LSA
      Link State ID: 3.3.3.3 (External Network Number)
      Advertising Router: 10.0.25.2
      LS Seq Number: 80000001
      Checksum: 0xcf99
      Length: 36

      Network Mask: /32
            Metric Type: 2 (Larger than any link state path)
            TOS: 0
            Metric: 20
            Forward Address: 10.0.23.3    <--- address copied from type-7 lsa
            External Route Tag: 0

    r2# sh ip os database

                    NSSA-external Link States (Area 0.0.0.1 [NSSA])

    Link ID         ADV Router      Age  Seq#       CkSum  Route
    3.3.3.3         10.0.23.3          8 0x80000001 0x431d E2 3.3.3.3/32 [0x0]

                    AS External Link States

    Link ID         ADV Router      Age  Seq#       CkSum  Route
    3.3.3.3         10.0.25.2          0 0x80000001 0xcf99 E2 3.3.3.3/32 [0x0]

    r2# conf t
    r2(config)# router ospf
    r2(config-router)# area 1 nssa suppress-fa
    r2(config-router)# exit
    r2(config)# exit

    r2# sh ip os database

                    NSSA-external Link States (Area 0.0.0.1 [NSSA])

    Link ID         ADV Router      Age  Seq#       CkSum  Route
    3.3.3.3         10.0.23.3         66 0x80000001 0x431d E2 3.3.3.3/32 [0x0]

                    AS External Link States

    Link ID         ADV Router      Age  Seq#       CkSum  Route
    3.3.3.3         10.0.25.2         16 0x80000002 0x0983 E2 3.3.3.3/32 [0x0]

    r1# sh ip os da external

           OSPF Router with ID (11.11.11.11)

                    AS External Link States

      LS age: 34
      Options: 0x2  : *|-|-|-|-|-|E|-
      LS Flags: 0x6
      LS Type: AS-external-LSA
      Link State ID: 3.3.3.3 (External Network Number)
      Advertising Router: 10.0.25.2
      LS Seq Number: 80000002
      Checksum: 0x0983
      Length: 36

      Network Mask: /32
            Metric Type: 2 (Larger than any link state path)
            TOS: 0
            Metric: 20
            Forward Address: 0.0.0.0       <--- address set to 0
            External Route Tag: 0

    r2# conf t
    r2(config)# router ospf
    r2(config-router)# no area 1 nssa suppress-fa
    r2(config-router)# exit

    r1# sh ip os da external

           OSPF Router with ID (11.11.11.11)

                    AS External Link States

      LS age: 1
      Options: 0x2  : *|-|-|-|-|-|E|-
      LS Flags: 0x6
      LS Type: AS-external-LSA
      Link State ID: 3.3.3.3 (External Network Number)
      Advertising Router: 10.0.25.2
      LS Seq Number: 80000003
      Checksum: 0xcb9b
      Length: 36
      Network Mask: /32
            Metric Type: 2 (Larger than any link state path)
            TOS: 0
            Metric: 20
            Forward Address: 0.0.0.0       <--- address set to 0
            External Route Tag: 0

    r2# conf t
    r2(config)# router ospf
    r2(config-router)# no area 1 nssa suppress-fa
    r2(config-router)# exit

    r1# sh ip os da external

           OSPF Router with ID (11.11.11.11)

                    AS External Link States

      LS age: 1
      Options: 0x2  : *|-|-|-|-|-|E|-
      LS Flags: 0x6
      LS Type: AS-external-LSA
      Link State ID: 3.3.3.3 (External Network Number)
      Advertising Router: 10.0.25.2
      LS Seq Number: 80000003
      Checksum: 0xcb9b
      Length: 36

      Network Mask: /32
            Metric Type: 2 (Larger than any link state path)
            TOS: 0
            Metric: 20
            Forward Address: 10.0.23.3    <--- address copied from type-7 lsa
            External Route Tag: 0

Signed-off-by: ckishimo <carles.kishimoto@gmail.com>

1 files changed, 27 insertions, 2 deletions

diff --git a/ospfd/ospf_lsa.c b/ospfd/ospf_lsa.c
index 6bde5467b..cb1c565d3 100644
--- a/ospfd/ospf_lsa.c
+++ b/ospfd/ospf_lsa.c
@@ -1765,7 +1765,14 @@ static struct ospf_lsa *ospf_lsa_translated_nssa_new(struct ospf *ospf,
 	/* copy over Type-7 data to new */
 	extnew->e[0].tos = ext->e[0].tos;
 	extnew->e[0].route_tag = ext->e[0].route_tag;
-	extnew->e[0].fwd_addr.s_addr = ext->e[0].fwd_addr.s_addr;
+	if (type7->area->suppress_fa) {
+		extnew->e[0].fwd_addr.s_addr = 0;
+		if (IS_DEBUG_OSPF_NSSA)
+			zlog_debug(
+				"ospf_lsa_translated_nssa_new(): Suppress forwarding address for %pI4",
+				&ei.p.prefix);
+	} else
+		extnew->e[0].fwd_addr.s_addr = ext->e[0].fwd_addr.s_addr;
 	new->data->ls_seqnum = type7->data->ls_seqnum;
 
 	/* add translated flag, checksum and lock new lsa */
@@ -1777,7 +1784,8 @@ static struct ospf_lsa *ospf_lsa_translated_nssa_new(struct ospf *ospf,
 
 /* Originate Translated Type-5 for supplied Type-7 NSSA LSA */
 struct ospf_lsa *ospf_translated_nssa_originate(struct ospf *ospf,
-						struct ospf_lsa *type7)
+						struct ospf_lsa *type7,
+						struct ospf_lsa *type5)
 {
 	struct ospf_lsa *new;
 	struct as_external_lsa *extnew;
@@ -1796,6 +1804,10 @@ struct ospf_lsa *ospf_translated_nssa_originate(struct ospf *ospf,
 
 	extnew = (struct as_external_lsa *)new->data;
 
+	/* Update LSA sequence number from translated Type-5 LSA */
+	if (type5)
+		new->data->ls_seqnum = lsa_seqnum_increment(type5);
+
 	if ((new = ospf_lsa_install(ospf, NULL, new)) == NULL) {
 		flog_warn(EC_OSPF_LSA_INSTALL_FAILURE,
 			  "%s: Could not install LSA id %pI4", __func__,
@@ -1823,6 +1835,8 @@ struct ospf_lsa *ospf_translated_nssa_refresh(struct ospf *ospf,
 					      struct ospf_lsa *type5)
 {
 	struct ospf_lsa *new = NULL;
+	struct as_external_lsa *extold = NULL;
+	uint32_t ls_seqnum = 0;
 
 	/* Sanity checks. */
 	assert(type7 || type5);
@@ -1887,6 +1901,12 @@ struct ospf_lsa *ospf_translated_nssa_refresh(struct ospf *ospf,
 		return NULL;
 	}
 
+	extold = (struct as_external_lsa *)type5->data;
+	if (type7->area->suppress_fa == 1) {
+		if (extold->e[0].fwd_addr.s_addr == 0)
+			ls_seqnum = ntohl(type5->data->ls_seqnum);
+	}
+
 	/* Delete LSA from neighbor retransmit-list. */
 	ospf_ls_retransmit_delete_nbr_as(ospf, type5);
 
@@ -1899,6 +1919,11 @@ struct ospf_lsa *ospf_translated_nssa_refresh(struct ospf *ospf,
 		return NULL;
 	}
 
+	if (type7->area->suppress_fa == 1) {
+		if (extold->e[0].fwd_addr.s_addr == 0)
+			new->data->ls_seqnum = htonl(ls_seqnum + 1);
+	}
+
 	if (!(new = ospf_lsa_install(ospf, NULL, new))) {
 		flog_warn(
 			EC_OSPF_LSA_INSTALL_FAILURE,